Cellular SPAR apparatus and method

ABSTRACT

According to various aspects of the invention, a buoyancy apparatus, a buoyancy system and a buoyancy method are provided. In one example embodiment of the present invention, a buoyancy apparatus for drilling and production caisson is provided for use in deep water offshore well operations. The buoyancy apparatus comprises a central cell, and a plurality of secondary cells essentially surrounding the central cell and secured to the central cell; wherein the perimeter surface of the buoyancy apparatus is essentially continuous along the length of at least the secondary cells. In one example embodiment, rigidly connecting the central cell and the secondary cells creates void chambers. The tops, bottoms, and sides, of the void chambers are sealed for buoyancy or production fluid storage. In another example embodiment, the void chambers have open bottoms. Another example embodiment comprises a mixture of sealed and open bottomed void chambers. In yet another example embodiment of the buoyancy apparatus comprises non-traditional curved shapes, rigidly connected. In alternate embodiments, any combination of the central cell, secondary cell, and the void chambers provide fixed ballast, variable ballast, buoyancy, or production storage as will occur to those of ordinary skill in the art.

BACKGROUND OF THE INVENTION

[0001] This invention is generally related to structures used offshorein drilling and production of hydrocarbons and more particularly tofloating vessels such as ships, semi-submersibles (e.g. SPARs), andtension leg platforms.

[0002] The SPAR platforms used in the offshore industry are deep draftfloating platforms that support heavy decks generally weighing from5,000 tons to 50,000 tons.

[0003] The SPARs typically range in length from 500 feet to 750 feet andin diameter from 70 feet to 150 feet. Methods of constructing SPARs aresimilar to ships with the axis of the cylinder being horizontal.Normally SPARs are constructed on land in a building berth whichcomprises a graving dock which can be flooded so the vessel can befloated out, or a dry-dock which can be submerged on slip-ways whichallows the vessel to slide down into the water, or on skid-ways whichallow the vessel to be skidded onto a launch barge. These methods andrelated equipment have been used for building ships for a long time.

[0004] Current practice has been to fabricate short segments of thecylinder and set these in a building berth where they are joinedtogether with a previous block until the structure reaches its fulllength. In a descriptive sense, it is like putting checkers together ona flat table to form an elongated cylinder. The structure is thenskidded out onto a barge or a heavy lift vessel where it is transportedto the installation site. This construction method has a number ofproblems. Some of these problems include the large diameter cylindricalsegments require very close tolerances to insure good welds at thejoints where the segments are joined together; a substantial number ofthe welded segments are out of position; a significant portion of theassembly must be performed high above the ground; the building dock mustsupport the fall weight of the structure; and the finished structuremust be skidded onto the transit vessel.

[0005] Attempts to solve these problems include U.S. Pat. No. 6,213,045B1; U.S. Pat. No. 4,702,321; U.S. Pat. No. 4,740,109; U.S. Pat. No.5,197,826; U.S. Pat. No. 5,443,330; U.S. Pat. No. 3,510,892; U.S. Pat.No. 3,360,810; U.S. Pat. No. 4,234,270; U.S. Pat. No. 4,630,968, andFrance 2,553,371. All of the previously-mentioned patents areincorporated herein by reference.

[0006] The '045 patent describes floatation tubes arranged in a varietyof configurations. The '321 patent describes an oil-storage caisson witha plurality of water-ballast compartments. The '109 patent describes amulti-tendon, buoyant tower. The '826 patent describes a buoyant towerfor flaring natural gas. The '330 patent describes a deep-water platformwith a single, buoyant flexible pile. The '892 patent describes afloating platform on a hollow cylinder with a flat disc to improvestability in swells. The '810 patent describes a single, buoyant tankfor buoyancy and storage of petroleum. The '270 patent describes anelastic, pre-stressed column with buoyancy tanks. The '968 patentteaches a method of constructing a buoyancy apparatus with a pluralityof cylinders. The '968 patent is the U.S. foreign-counterpartapplication for the '371 French patent. There is a long felt need for animprovement to the classic SPAR design with many compartments, fixed andvariable ballast, possible production fluid storage, buoyancy chambers,and an improved method of constructing a buoyancy apparatus.

SUMMARY OF THE INVENTION

[0007] According to various aspects of the invention, a buoyancyapparatus, a buoyancy system, and a buoyancy method are provided. In oneexample embodiment, a buoyancy apparatus for drilling and productioncaisson is provided for use in deep water offshore well operations. Thebuoyancy apparatus comprises a central cell, and a plurality ofsecondary cells essentially surrounding the central cell and secured tothe central cell; wherein the perimeter surface of the buoyancyapparatus is essentially continuous along the length of at least onesecondary cell. Rigidly connecting the central cell and the secondarycells creates void chambers. The tops, bottoms, and sides, of the voidchambers are sealed for buoyancy or production fluid storage. In anotherexample embodiment, the void chambers have open bottoms. Still a furtherexample comprises a mixture of sealed and open bottomed void chambers.In yet another embodiment, the buoyancy apparatus comprisesnon-traditional curved shapes, rigidly connected. Any combination of thecentral cell, secondary cell, and the void chambers provide fixedballast, variable ballast, buoyancy, or production storage as will occurto those of ordinary skill in the art.

[0008] In a further aspect of the present invention, a method ofconstructing a buoyancy apparatus is provided, the method comprises:attaching a central cell to a first secondary cell with a firstelongated member; attaching a second secondary cell to the firstsecondary cell and the central cell with a second elongated member and athird elongated member, thereby creating a void chamber between thecentral cell, the first secondary cell, and the second secondary cell;and continuing to attach a plurality of secondary cells to the centralcell with a plurality of elongated members, until a loop of secondarycells and a plurality of void chambers are formed.

[0009] In a further aspect, a buoyancy apparatus for a drilling andproduction caisson for use in deep water offshore well operations isprovided. The buoyancy apparatus comprises a central elongated cell,defining a center well, an elongated member connected to the centralcell on one end and connected at the other end on a secondary cell or ona secondary elongated member. The secondary cell or secondary elongatedmember is directly connected to the central cell or is connected to thecentral cell through a succession of complimentary elongated membersand/or complimentary cells, wherein said cells and/or elongated membersunaccompanied or in combination with each other define an elongatedchamber. The cells and/or elongated chambers are used for buoyancy orvariable ballast, or a combination of thereof.

[0010] Further objects and advantages of the invention will be readilyapparent from the various examples below. Variations of these examplesare within the scope and spirit of the invention.

BRIEF DESCRIPTION OF THE FIGURES

[0011]FIG. 1 shows an example embodiment of the present invention havinga platform configuration with seven cells connected using void chambersbetween the cells for buoyancy.

[0012]FIG. 2 shows a cross-sectional view of the platform configurationwith seven cells connected using void chambers between the cells forbuoyancy.

[0013]FIG. 3 shows a plan view of an example embodiment having aplatform configuration with nineteen cells connected using void chambersbetween the cells for buoyancy.

[0014]FIG. 4 shows a side view of an example embodiment of wet dockconstruction of a buoyancy apparatus using a support beam.

[0015]FIG. 5 shows a side view of an example embodiment of a wet dockconstruction of a buoyancy apparatus using dockside cranes.

[0016]FIG. 6 shows a side view of an example embodiment of a wet dockconstruction of a buoyancy apparatus using dockside cranes with onesecondary cell.

[0017]FIG. 7 shows a side view of an example embodiment of a wet dockconstruction of a buoyancy apparatus using dockside cranes with twosecondary cells.

[0018]FIG. 8 shows a side view of an example embodiment of a wet dockconstruction of a buoyancy apparatus using dockside cranes with threesecondary cells.

[0019]FIG. 9 shows a side view of an example embodiment of a wet dockconstruction of a buoyancy apparatus using dockside cranes with fivesecondary cells.

[0020]FIG. 10 shows a side view of an example embodiment of a wet dockconstruction of a buoyancy apparatus using dockside cranes with sixsecondary cells.

[0021]FIG. 11 shows a side view of an example embodiment of a wet dockconstruction of a buoyancy apparatus using dockside cranes with onecentral cell and seven secondary cells.

[0022]FIG. 12 shows a cross-sectional view of an example embodimentcomprising a central cell, eight secondary cells, void chambers,elongated members and shaped members.

[0023]FIG. 13 shows a cross-sectional view of an example embodiment withvariable curvature.

[0024]FIG. 14 shows a cross-sectional view of an example embodiment withconstant curvature.

[0025]FIG. 15 shows an example embodiment using a π-core construction.

[0026]FIG. 16 shows further aspects of an example embodiment of thepresent invention having interstitial chamber compartments.

[0027]FIG. 17 shows a further example embodiment having egg-shapedsecondary cells.

DETAILED DESCRIPTION EXAMPLE EMBODIMENTS OF THE INVENTION

[0028] In one example embodiment of the present invention, a buoyancyapparatus for drilling and production caisson is provided for use indeep water offshore well operations. As illustrated in FIG. 1, thebuoyancy apparatus comprises a central cell 120, and a plurality ofsecondary cells 130 essentially surrounding the central cell 120 andsecured to the central cell.

[0029] In a further embodiment, the perimeter surface 190 of thebuoyancy apparatus is essentially continuous along the length 170 of atleast the secondary cells 130. As those of ordinary skill in the artwill recognize the perimeter is essentially continuous because holes arefound in various embodiments to allow the flow of water in and out ofthe cells and chambers. In a further embodiment, the buoyancy apparatus100 further comprises at least one elongated member 140 connecting thecentral cell 120 and at least one secondary cell 130. Those of ordinaryskill in the art will recognize that while the perimeter surface 190 maycomprise the connection and combination of many different cells 120 ,130 or elongated members 150, because the cells 120 , 130 or elongatedmembers 150 are connected along the length 170 of at least one of thesecondary cells 130, an essentially continuous surface 190 is formed.

[0030] In a further embodiment, the central cell 120, the secondarycells 130 and the elongated members 140 create void chambers 150 betweenthe outside of the central cell 120, the outside of at least onesecondary cell 130, and the elongated member 140.

[0031] In a further embodiment, illustrated in FIGS. 1 and 2, thecentral cell 120 and the secondary cells 130 further comprise anelongated tubular cell. In a further embodiment, the elongated members140 comprise metal surfaces rigidly connecting the central cell 120 andat least one secondary cell 130. Of course in alternate embodiments, thecentral cell 120, the secondary cell 130, the void chambers 150, and theelongated members 140 comprise various shapes and sizes as will occur tothose of ordinary skill in the art.

[0032] In alternate embodiments, any combination of the central cell120, secondary cell 130, and void chambers 150 provide buoyancy,production fluid storage, variable ballasts, or fixed ballasts or anyother function that will occur to those of ordinary skill in the art. Inalternate embodiments, the central cell 120, secondary cells 130, or thevoid chambers 150 further comprises pumps, valves, or any other devicethat will occur to those of ordinary skill in the art to control theballast or to control and adjust the buoyancy of the apparatus 100 whilein use.

[0033] In the illustrated example, the central cell 120 and thesecondary cell 130 comprise substantially the same diameter cells.Example storage capacity of the buoyancy apparatus 100 with uniform sizecell diameters for the central cell 120 and the secondary cell 130 andcell lengths of 550 feet are seen in the Table 1, below: Oil StorageCapacity Cell Diamter (feet) Weight (tons) (Barrels) 50 18,000 1,100,00045 16,000 900,000 40 13,500 704,000 35 12,000 539,000 30 10,000 400,00025 8,000 275,000

[0034] In one example embodiment, the buoyancy apparatus 100 will floatan estimated fifty-feet above the water surface 110. The bottom of thebuoyancy apparatus 100 will be submerged about five hundred feet belowthe water surface 110.

[0035] An example embodiment illustrated in FIG. 2 shows a cross-sectionof the buoyancy apparatus 100 shown in FIG. 1 with seven substantiallyequal diameter cells 120, 130. FIG. 2 shows an embodiment of thebuoyancy apparatus 100 with the central cell 120 centrally located,surrounded by six secondary cells 130 with the central cell 120 and thesecondary cells 130 rigidly connected with the plurality of elongatedmembers 140. The elongated members 140 provide a seal along asubstantial portion of the entire length of the central cell 120 and thesecondary cells 130.

[0036] In some embodiments, the central cell 120, the secondary cells130, and the elongated members 140, comprise metal, while, in otherembodiments, the central cell 120, the secondary cells 130 and theelongated members 140 comprise non-metal.

[0037] The central cell 120, the secondary cells 130, and the elongatedmembers 140 are rigidly connected in some embodiments, by attachingmeans (for example, ties and other connectors).

[0038] In another example embodiment, the buoyancy apparatus 100comprises cells having unequal diameters. For example, the cells 120 and130 comprise different diameters.

[0039] Referring to FIG. 3, in a further example embodiment, nineteensubstantially equal diameter cells form a buoyancy apparatus 100 in ahexagon shape. A central cell 120 connects to six secondary cells 130with a plurality of elongated members 140, forming a plurality of voidchambers 150. The six secondary cells 130 connect to twelve additionalsecondary cells 130 with additional elongated members 140 to createadditional void chambers 150.

[0040] In various embodiments, the void chambers 150 function in amanner similar to the cells 120, 130 with pumps and valves to controlthe buoyancy of the void chamber 150, in order to affect the buoyancy ofthe buoyancy apparatus 100. The weight of the buoyancy apparatus 100will change as production fluid is produced and stored in the voidchambers 150, the central cell 120 and the secondary cells 130. Thebuoyancy is adjustable, to accommodate the weight of the productionfluid. The configuration of FIG. 3 comprises a high degree ofcompartmentalization. Compartmentalization diversifies risks of failureof the system as a whole because other chambers compensate for onefailed chamber. As a result, the failure of one chamber will haveminimal change on the overall draft or stability of the buoyancyapparatus 100 compared to non-compartmentalized vessels.

[0041] As will occur to those of ordinary skill in the art, thenineteen-cell embodiment enables the use of smaller cells than neededfor the seven-cell embodiment with the same amount of buoyancy. Smallercells require smaller cranes to construct the buoyancy apparatus 100.

[0042] As illustrated in FIG. 12, in a further embodiment, the buoyancyapparatus 100 further comprises at least one shaped member 1260. In afurther embodiment, at least one end of the shaped member 1260 issecured to a secondary cell 130. In alternate embodiments, the shapedmembers 1260 are curved, straight or any other shape that will occur tothose of ordinary skill in the art. As will occur to those of ordinaryskill in the art, in alternate embodiments, the combination of thecentral cell 120, the secondary cells 130, the shaped members 1260 andthe elongated members 150 create void chambers 150 of varying shapes andsizes between the outside of the central cell 120, the outside of thesecondary cell 130, the shaped members 1260 and the elongated members150.

[0043] In a further embodiment, illustrated in FIG. 16, the buoyancyapparatus 100 further comprises interstitial chambers 1680 between thecentral cell 120 and the secondary cells 130. In a further embodiment,the buoyancy apparatus 100 further comprises water openings 1690 in theinterstitial chambers 1680. In still a further embodiment, the centralcell 120, secondary cell 130 and interstitial chambers 1680 are dividedinto compartments 1685, 1645. In some embodiments, the cylindricalcompartments 1645 (central cell 120 and secondary cell 130) are forbuoyancy only and are assembled at atmospheric pressure. In an evenfurther embodiment, the interstitial chamber compartments 1685 are openat each of their respective bottoms 1690 to the hydrostatic pressurefrom the ocean 110. Of course, in alternate embodiments, any cell isopen to the sea at its respective bottom. Furthermore, in furtherembodiments, a plurality of horizontal bulkheads in any of the secondarycells, elongated chambers, or interstitial chambers are provided. Inmost embodiments, the central cell comprises a center well and is open.In further embodiments, to control the water level inside thecompartments 1685, air is pumped in and out of the top of thecompartment with an air pump 1695. This accomplishes three things: (1)the pressure gradient is minimized between the inside of eachinterstitial chamber 1680 and the hydrostatic pressure of the sea 110,(2) a means for variable ballast is provided, (3) and pressure gradientbetween the interstitial chamber compartment 1685 and the central cell120 and secondary cells 130 is minimized on a global scale. In furtherembodiments, each cylindrical compartment 1645 (central cell 120 andsecondary cell 130) is designed for a specific pressure gradientdepending on the nominal water depth at which it is located. It is lessexpensive to design a cylindrical shape for pressure than anon-cylindrical shape (e.g. the interstitial spaces), which is why insome embodiments, the interstitial chamber compartments 1685 arepressurized with air to reduce the pressure gradient. In furtheralternate embodiments, any combination of the central cell 120, thesecondary cell 130, the void chambers 150, and the interstitial chambercompartments 1685, and cylindrical compartments 1645 comprise productionfluid storage, buoyancy, fixed ballast, variable ballast or any otherfunction that will occur to those of ordinary skill in the art.

[0044] In a further embodiment, a “π-core” construction of a buoyancyapparatus 100 is provided. As illustrated in FIG. 15, a furtherembodiment comprises a plurality of the secondary cells 130 essentiallysurround the central cell 120. In a further embodiment, the secondarycells 130 comprise an outer or curved longitudinal surface 1535, and atleast one radial surface 1525. In a further embodiment, the plurality ofsecondary cells 130 essentially surround the central cell 120. In afurther embodiment, the radial surface 1525 and the longitudinal surface1535 are essentially perpendicular.

[0045] In a further embodiment, the at least one radial surface 1525 isconnected to the central cell 120 without an inner surface 1515. Inalternate embodiments, various shapes of the “π-core” construction areused such as gamma-shaped outer surfaces, tau-shaped outer surfaces orany other shape that will occur to those of ordinary skill in the art.For example, in a gamma-shaped (Γ) embodiment, a radially extendingmember and a longitudinally extending member are provided. The radiallyextending member and the longitudinally extending member are essentiallyperpendicular. In alternate embodiments, the radially extending memberand the longitudinally extending member are straight, curved, or anyother shape that will occur to those of ordinary skill in the art. Instill a further embodiment, a tau shaped (T) embodiment is provided. Atau-shaped embodiment comprises a radially extending member and one ortwo members essentially perpendicular to said radial member. The radialmember and the essentially perpendicular members are, in alternateembodiments straight, curved, or any other shape that will occur tothose of ordinary skill in the art.

[0046] In a further embodiment, illustrated in FIGS. 13 and 14, abuoyancy apparatus 100 further comprises a plurality of secondary cells130. In a further embodiment, the secondary cells 130 essentiallysurround the central cell 120. In a further embodiment, at least one end1365 of the secondary cell 130 is secured to the central cell 120 and atleast one other end 1375 is secured to another secondary cell 130. In afurther embodiment, the connection of the secondary cells 130 creates anessentially continuous perimeter surface 190. In a further embodiment,the secondary cell 130 comprises an inner surface 1385 and an outersurface 1395. In a further embodiment, the sum of the inner surfaces1385 essentially create the central cell 120. In still a furtherembodiment, the sum of the outer surfaces 1395 comprise an essentiallycontinuous perimeter surface 190. In a further embodiment, the secondarycells 130 comprise an outer surface 1395 and a radial surface 1345 withno inner surface 1385. In a further embodiment, the radial surface 1345is directly connected to the central cell 120 and the outer surface 1395is connect to another secondary cell 130.

[0047] In a further embodiment, illustrated in FIG. 14, the secondarycell 130 comprises a single curved surface 1400, wherein one end 1365 ofthe curved surface 1415 is directly connected to the central cell 120and the other end 1375 is connected to another secondary cell 130. In afurther embodiment, the sum of inner surfaces 1415 essentially createthe central cell 120. In a further embodiment, the connection of thesecondary cells 130 creates a continuous perimeter surface 190.

[0048] In another example embodiment, as illustrated in FIG. 17, thecells comprise elliptical or egg shape cross sections. Of course, inalternate embodiments the cells are various shapes as will occur tothose of ordinary skill in the art. In a further embodiment, thebuoyancy apparatus further comprises a cylinder 1710 surrounding thecentral cell 120 and the at least one secondary cell 130.

[0049] According to a further aspect of the invention, a method ofconstructing a buoyancy apparatus is provided. The method comprisesattaching a central cell 120 to a first secondary cell 130 with a firstelongated member 140, attaching a second secondary cell 130 to the firstsecondary cell 130 and the central cell 120 with a second elongatedmember 140 and a third elongated member 140, thereby creating a voidchamber 150 between the central cell 120, the first secondary cell 130,and the second secondary cell 130, and continuing to attach a pluralityof secondary cells 130 to the central cell 120 with a plurality ofelongated members 140, until a loop of secondary cells 130 and aplurality of void chambers 150 are formed. According to a further aspectof the invention, assembly of various examples seen above is provided,in one example, as seen in FIG. 4. A central cell 120 is held by aplurality of supports 410 on a support beam 420 that supports thecentral cell 120. In addition, the water partially supports the centralcell 120. The support beam 420 moves with a pulley system comprising awinch cable 450, a dock pulley 460, a beam pulley 470 and a winch 480.The beam pulley 470 connects to the support beam 420. The dock pulley460 connects to a dock wall 430. The winch 480 mounts on a dock surface465. The dock surface 465 connects to the dock wall 430, which connectsto a dock bottom 440. The winch cable 450 runs through the dock pulley460, the beam pulley 470 to the winch 480, whereby the winch 480 movesthe support beam 420 vertically. Although not shown, the plurality ofpulley systems are used, one at each end of the support beam 420.

[0050] In another example embodiment, a plurality of support beams 420are spaced at selected distances to prevent the central cell 120 frombeing over stressed by a single beam 420. The elevation of the pluralityof support beams 420 is adjusted as needed to keep the central cell 120from being over-stressed as the assembly continues. The support 410 andthe weight of the central cell 120 is set to prevent the central cell120 from moving as a result of wave, wind, and tidal forces.

[0051] In still another example embodiment, adding or removing ballastwater from the cells 120, 130 controls the buoyancy of the buoyancyapparatus 100. The combination of ballast water and the elevation of thesupport beam 420 give the wet dock a great deal of flexibility forconstructing, assembling, and repairing certain types of the buoyancyapparatuses 100 at relatively low cost.

[0052]FIG. 5 shows an example embodiment of wet dock construction usingcranes. The central cell 120 supports the secondary cell 130 attached tothe central cell 120 with the elongated members 140. Water in the wetdock supports the central cell 120. A first crane-cable-connection 500and a second crane-cable-connection 505 stabilize the central cell 120.The first crane-cable-connection 500 connects a first crane cable 510 tothe central cell 120. On the other side of the central cell 120, thesecond crane-cable-connection 505 connects a second crane cable 515 tothe central cell 120. The first crane cable 510 connects to a firstcrane 520. The first crane 520 controls the first crane cable 510 with afirst crane boom 530. In addition, the first crane 520 controls thelength of the first crane cable 510. The second crane cable 515 connectsto a second crane 525, with a second crane boom 535 to control thesecond crane cable 515. The second crane 525 also controls the length ofthe second crane cable 515. The first crane 520 and the second crane 525are on the dock surface 465. Although not shown, in reality, more thantwo cranes hold the buoyancy apparatus 100.

[0053] In another example embodiment, the central cell 120 rests againstthe dock wall 430 to stabilize the central cell 120. In another exampleembodiment, ballast water aids the buoyancy of the buoyancy apparatus100.

[0054] However the buoyancy apparatus 100 is supported, the example ofFIG. 6 shows an example of a method of wet dock construction providedaccording to the present invention. The buoyancy apparatus 100 isrotated with the first crane cable 510 connected to a third cableconnection 600 and the second crane cable 515 connected to a fourthcable connection 610 making room for another secondary cell 130 to beconnected on the buoyancy apparatus 100. In FIG. 7, another secondarycell 130 is transported by another crane (not shown) on top of thebuoyancy apparatus 100 to be joined to the buoyancy apparatus 100. Thesecond crane cable 515 connects to the fourth cable connection 610 andthe first crane cable 510 connects to a fifth cable connection 700.Turning now to FIGS. 8-11, the buoyancy apparatus 100 is again rotatedwith the cables making room for another secondary cell 130 to beconnected on the buoyancy apparatus 100 one at a time until the centralcell 120 is essentially surrounded by secondary cells 130. In anotherexample embodiment, a second ring of secondary cells 130 encircle thefirst ring of secondary cells 130 attached to the central cell 120 asshown in FIG. 3.

[0055] Various cable connections allow cranes to transport the secondarycells 130 to the buoyancy apparatus 100 for construction. The varioustransport cable connections are used to control the buoyancy apparatus100 after the secondary cell 130 is rigidly connected to the buoyancyapparatus 100. Other embodiments use various numbers of cranes in theconstruction method.

[0056] The benefits of the construction methods comprise: minimizing outof position welding, reducing foundation loads, lift-load requirements,launching problems, and that in some example embodiments, theconstruction is not completed at relatively high elevations as is thecase with classic SPAR construction methods. In even further alternateembodiments, for example, multiple cranes 520, 525crane-cable-connection 500, 505 and crane booms 530 or any otherequipment that will occur to those of ordinary skill in the art are usedto secure, rotate and attach the cells 120, 130, and elongated members140. In alternate embodiments, the cells 120, 130, and elongated members140 are attached by welding, gluing or any other method that will occurto those of ordinary skill in the art.

[0057] Those of ordinary skill in the art will appreciate that inalternate embodiments, each embodiment of the buoyancy apparatus 100 isconstructed using any combination of the construction methods describedabove or any other construction method that will occur to those ofordinary skill in the art.

[0058] Turning to a method aspect of the invention, a method isdisclosed for a method of providing buoyancy for a hydrocarbon wellplatform. The method comprises isolating a first curved volume from thepressure, isolating a second curved volume from the pressure, isolatinga third curved volume from the pressure with the first and the secondvolumes, and isolating a fourth curved volume from the pressure, whereeach of the curved volumes is continuous.

[0059] In some embodiments, isolating the curved volume comprisesrigidly connecting a plurality of cell plates together, whereby creatinga void chamber between the cell plates. The means for isolating a curvedvolume comprises rigidly connecting a plurality of cell plates with acentral volume. The cell plates comprise in various embodiments,variable curvature cell plates (FIG. 13) and constant curvature cellplates (FIG. 14). Such means are described above with reference to FIGS.4-11 and further include welds, glue, clamps, ties, and otherconnectors, as will occur to those of skill in the art.

[0060] Yet another aspect of the invention comprises a method ofconstructing a SPAR platform. The method comprises a plurality ofbuoyancy cells together with a plurality of elongated members, therebycreating a plurality of void chambers between the buoyancy cells.

[0061] According to another example embodiment, a method of providingbuoyancy for a hydrocarbon well platform is provided. The methodcomprises isolating a plurality of curved volumes from the pressure. Thecurved volumes form a continuous structure. In a further embodiment, themethod comprises isolating a plurality of cylindrical volumes from thepressure.

[0062] In a further embodiment, a method of providing buoyancy for ahydrocarbon well platform is provided. The method comprises isolating afirst curved volume from external pressure, wherein the isolating afirst curved volume provides at least a partial support capacity for awell platform, isolating a second curved volume from external pressurewherein the isolating a second curved volume provides at least a partialsupport capacity for a well platform, isolating a third curved volumefrom external pressure, wherein the isolating a third curved volumeprovides at least a partial support capacity for a well platform, andisolating a fourth curved volume, with the first, second, and thirdvolumes, from pressure.

[0063] In a further embodiment, the isolating a fourth curved volumecomprises surrounding a central volume with the first, second, and thirdvolumes. In a further embodiment, the curved volumes comprise variablecurvature shaped curved volumes. In still a further embodiment, thecurved volumes comprise substantially uniform shape curved volumes. In afurther embodiment, the curved volumes comprise constant curvature shapecurved volumes.

[0064] In a further embodiment, a system of providing buoyancy for ahydrocarbon well platform is provided. The system comprises a means forisolating a first curved volume from the pressure, a means for isolatinga second curved volume from the pressure, a means for isolating a thirdcurved volume from the pressure with the first and the second volumes,and a means for isolating a fourth curved volume from the pressure,where each of the curved volumes is continuous. In a further embodiment,the curved volumes comprise constant curvature curved volumes. In afurther embodiment, the curved volumes comprise substantially uniformsize volumes. In a further embodiment, the curved volumes comprisevariable curvature curved volumes. In a further embodiment, the curvedvolumes comprise substantially uniform size volumes. In a furtherembodiment, the system further comprises a means for isolating a centralcylindrical volume. In a further embodiment, the curved volumes compriseconstant curvature curved volumes. In a further embodiment, the meansfor isolating comprises welding. In a further embodiment, the curvedvolumes comprise variable curvature curved volumes. In a furtherembodiment, the means for isolating a first curved volume comprises acell. In a further embodiment, the means for isolating a second curvedvolume comprises a cylinder. In a further embodiment, the means forisolating a third curved volume comprises a cylinder.

[0065] In a further embodiment, a buoyancy apparatus is provided foroffshore petroleum well platforms. The apparatus comprises a centralelongated buoyancy cell, a first secondary elongated buoyancy cellconnected with a first elongated member to the central elongatedbuoyancy cell, a second secondary elongated buoyancy cell connected tothe first secondary elongated buoyancy cell and the central elongatedbuoyancy cell with a second elongated member and a third elongatedmember, wherein a void chamber is defined between the center, the first,and the second elongated buoyancy cells.

[0066] Although the description above contains many example embodiments,these merely provide illustrations and should not be construed asexhaustive the scope of the invention. Further objects and advantages ofthe invention will be readily apparent from the various exampleembodiments.

I claim:
 1. A buoyancy apparatus for a drilling and production caissonfor use in deep water offshore well operations, comprising: a) a centralelongated cell defining a center well; b) an elongated member connectedto the central cell on one end and connected at the other end on asecondary cell or on a secondary elongated member; c) said secondarycell or secondary elongated member being directly connected to thecentral cell or being connected to the central cell through a successionof complimentary elongated members and/or complimentary cells, whereinsaid cells and/or elongated members unaccompanied or in combination witheach other define an elongated chamber; d) wherein said cells and/orelongated chambers are used for buoyancy or variable ballast, or acombination of thereof.
 2. The buoyancy apparatus of claim 1, wherein aperimeter surface of the buoyancy apparatus is essentially continuousalong the length of at least one elongated chamber.
 3. The buoyancyapparatus of claim 1, wherein the perimeter comprises openings for waterflow.
 4. The buoyancy apparatus of claim 1, wherein said elongatedchambers further comprise void chambers.
 5. The buoyancy apparatus ofclaim 1, wherein said secondary cell further comprises a circularcross-section.
 6. The buoyancy apparatus of claim 1, wherein saidsecondary cell further comprises a non-circular cross-section.
 7. Thebuoyancy apparatus of claim 6,wherein said secondary cell furthercomprises an egg-shaped cross-section.
 8. The buoyancy apparatus ofclaim 1, wherein the elongated members comprise metal surfaces.
 9. Thebuoyancy apparatus of claim 1, further comprising a plurality ofelongated members comprising curved shapes essentially surrounding thecentral cell; wherein one end of each elongated member is secured to thecentral cell and the other end of each elongated member is secured to asecondary elongated member.
 10. The buoyancy apparatus of claim 1,wherein the elongated member further comprises a radial elongated memberand the secondary elongated member further comprises a longitudinalelongated member; wherein said radial elongated member is essentiallyperpendicular to said longitudinal elongated member.
 11. The buoyancyapparatus of claim 10, further comprising π-shaped cells essentiallysurrounding the central cell.
 12. The buoyancy apparatus of claim 1,further comprising an interstitial chamber.
 13. The buoyancy apparatusof claim 12, further comprising a bulkhead within said interstitialcell.
 14. The buoyancy apparatus of claim 12, further comprising a wateropening in the interstitial chamber.
 15. The buoyancy apparatus of claim14, further comprising an air pump.
 16. The buoyancy apparatus of claim1, further comprising a bulkhead within said secondary cell.
 17. Thebuoyancy apparatus of claim 1, further comprising a water opening atessentially the bottom of the secondary cell.
 18. The buoyancy apparatusof claim 1, further comprising a bulkhead within said elongated chamber.19. The buoyancy apparatus of claim 1, further comprising a wateropening at essentially the bottom of the elongated chamber.
 20. A methodof constructing a buoyancy apparatus, the method comprising: attaching acentral cell to a first secondary cell with a first elongated member,attaching a second secondary cell to the first secondary cell and thecentral cell with a second elongated member and a third elongatedmember, thereby creating a void chamber between the central cell, thefirst secondary cell, and the second secondary cell, and continuing toattach a plurality of secondary cells to the central cell with aplurality of elongated members, until a loop of secondary cells and aplurality of void chambers are formed.
 21. The method of claim 20wherein: the central cell and the secondary cells comprise substantiallyelongated cells, the central cell is supported lengthwise in water, andthe central cell is rotated between the attaching the central cell tothe first secondary cell and the attaching the second secondary cell tothe first secondary cell.
 22. The method of claim 21, wherein thesecondary cell buoyancy cells comprise metal.
 23. The method of claim21, wherein the attaching comprises welding.
 24. The method of claim 21,wherein the secondary cells comprise composites.
 25. The method of claim21, wherein the attaching comprises gluing.